1. Field of the Invention
The present invention relates generally to a system and method for providing a steering control for an autonomous vehicle. The autonomous vehicle of the present invention runs autonomously on the basis of a road contour index detected by a photograph device, such as a video camera.
2. Description of the Background Art
U.S. patent application Ser. No. 07/485,910, now U.S. Pat. No. 5,122,957, which has been filed on Feb. 27, 1990 and recently allowed exemplifies a first previously proposed autonomous vehicle.
In addition, U.S. patent application Ser. No. 07/337,707, filed on Apr. 13, 1989, now U.S. Pat. No. 5,229,941, exemplifies a second previously proposed autonomous vehicle.
Furthermore, Japanese Patent Application First Publication No. Heisei 2-270005 published on Nov. 5, 1990 (which corresponds to U.S. patent application Ser. No. 07/507,572, now U.S. Pat. No. 5,101,351, which has been filed on Apr. 11, 1990 and has recently been allowed) exemplifies a third previously proposed autonomous vehicle in which a camera is mounted on the vehicle for photographing a white line extended along the running road or a side edge of the running road and a steering wheel of the vehicle is controlled so as to run the vehicle substantially in parallel to the photographed white line.
In the third previously proposed autonomous vehicle, the autonomous vehicle runs automatically with the accurate steering control achieved over a complex curved road on the basis of positions of the white line at a multiple number of measuring points of location placed ahead of the vehicle.
In addition, in the third previously proposed autonomous vehicle, the autonomous vehicle can accurately run on a center position of the road which is in the form of the letter S, as compared with the case in which the run of the vehicle is based on a single measuring point of information including a white line position at a constant distance from a forward local range of the vehicle.
However, it becomes difficult to maintain the accuracy of the control over the steering movement according to the photographed image of the road shape index such as the white line, e.g., when a shadow of a building located near the ground of road rests thereon and recognition of the white line becomes impossible, or when the position of white line at the measuring point of location is out of range of the photographing camera.
In order to compensate for such deficiencies as described above, the number of measuring points may be set by a multiple number of points of locations so that a bad effect of lacking a single or two points of measuring points at which the information of the white line can be obtained can be minimized. However, since it is uncertain where an interruption of the series of road shape index occurs, the settings of the measuring points needs to be close to each other. However, the information at the additively increased measuring points are usually not necessary and not used. In addition, a large capacity of memory for storing the measurement information is simultaneously required in a steering control device of the autonomous vehicle and the processing speed of the control device are reduced.